This invention relates to an adjustment prevention mechanism of a carburetor provided with a adjustment device for adjusting idling revolution or air-fuel ratio.
As known, carburetors of gasoline engines as used, for example, in automobiles are provided with air-fuel ratio control devices such as devices for adjusting fuel in idling. Such adjustment devices are adjusted so that the air-fuel ratio will be most suitable for idling, by carburetor makers, automobile makers, or automobile sale dealers. However, there are instances where the adjustment devices are readjusted so that the precisely adjusted air-fuel ratio will become improper after transferred to users. As the results, dangers such as an increase of harmful components of exhaust gas from an engine, improper engine operation, or increased expenditure of fuel may be brought about.
In Japanese Laying-open of Patent Application No. 35540/1975, two means for preventing readjustment of the above mentioned adjustment device, such as an adjusting screw are disclosed. In one of the means shown in FIG. 1 of the Japanese application, a cap 13 is provided on a head 9 of an adjusting screw 6 so that the cap can be rotated relatively to the head 9. The Japanese Laying-open discloses that even if users rotate the cap 9, the adjusting screw 6 is not rotated because torque of the cap 9 is not transmitted to the adjusting screw 6 whereby the readjustment of the means by the users is prevented. However, with this arrangement there is a danger that the cap 13 may be pulled out from the head 9 of the screw 6, or that rotation of the cap 13 may follow that of the screw 6 if the cap 13 is fairly strongly clutched. Another means for preventing readjustment of the adjustment device is described in FIG. 2, 3 and 4 of the above-mentioned Japanese application. This arrangement has a finger-shaped element 16 on the cap 13a. The element 16 is inserted in a hole 17 made in a side wall of a carburetor body so that the cap 13a is not rotated. However, the means also has a danger such that the cap 13a may pulled out from the head 9 of the screw 6.
Thus, there is no readjustment prevention mechanism which can satisfactorily prevent the readjustment of the adjustment device by users.